With the advent of the Internet and the World Wide Web (WWW), the need for high-speed transmission of data including video and audio has continued to increase. Moreover, in addition to the demand for higher bandwidth, there has also been an increased need for various types of services that employ different protocols. For example, certain customers (e.g., companies providing voice services) of high-speed networks want to operate on a Time Division Multiplexing (TDM) Network, which combines different data streams, such as voice traffic, such that each data stream is assigned a time slot within the combined data stream. Moreover, other customers of high-speed networks may desire to transport data employing packet-based data streams, which do not have dedicated timeslots to given packets. Examples of the types of packets that can be placed into such data streams can include Asynchronous Transfer Mode (ATM). Internet Protocol (IP), Frame Relay, voice over IP and Point-to-Point Protocol (PPP).
FIG. 1 illustrates a prior art traffic or line card within a network element for processing of packet-based data that is wrapped in different formats for transmission. In particular, FIG. 1 includes line card 100 that includes receiving unit 120 and transmitting unit 122. Receiving unit 120 includes deframer unit 102 that is coupled to packet engine unit 104, which in turn is coupled to packet processor 106. Transmitting unit 122 includes packet processor 108 that is coupled to packet engine unit 110, which in turn is coupled to framer unit 112. The packet-based data being received by and transmitted out from deframer unit 102 and framer unit 112, respectively, is encapsulated or wrapped into different formats or protocols. For example, one type of such format could include Synchronous Optical Network (SONET) and Synchronous Digital Hierarchy (SDH).
Within receiving unit 102, deframer unit 102 receives the encapsulated packet-based data and removes the payload of this encapsulated data, which is the packet-based data. Deframer unit 102 then forwards this payload to packet engine unit 104. Packet engine unit 104 locates the packet boundaries within the payload and forwards the packets to packet processor 106. Accordingly, packet processor 106 can perform various packet operations on such packets. For example, if the packets are Internet Protocol (IP) packets, packet processor 106 can include a forwarding table for forwarding these IP packets to other locations within the network that contains the network element that includes line card 100.
Within transmitting unit 122, packet processor 108 receives packets from other locations in the networks, such as IP routers for IP packets, and forwards such packets to packet engine unit 110. Packet engine unit 110 combines these packets into payloads of the protocol associated with the transmitting line coupled to framing unit 112. Packet engine unit 110 then forwards these payloads to framer unit 112. Framer unit 112 then encapsulates these payloads into the protocol for the transmitting line and forwards these encapsulated payloads thereon.
FIG. 2 illustrates a different prior art traffic or line card within a network element for processing of TDM traffic, including telephone calls, through a packet-based network. In particular, FIG. 2 includes line card 200 that allows for voice over IP and includes receiving unit 220 and transmitting unit 222. Receiving unit 220 includes deframer unit 202 that is coupled to interface unit 204 that is coupled to digital signal processor 206, which in turn is coupled to packet processor 208. Transmitting unit 222 includes packet processor 210 that is coupled to digital signal processor 212 that is coupled to interface unit 214, which in turn is coupled to framer unit 216.
The input into receiving unit 220 is TDM carrying telephone lines, such as Data Signal (DS)-3s and DS1s. In particular, 24 DS0 data streams, each associated with a given telephone call, are interleaved within a DS1. Moreover, under current transmission standards, 28 DS1 data streams can be interleaved into a single DS3. Deframer unit 202 receives the DS3s or DS1s and removes the DS0s contained therein. Moreover, the DS3 and DS1 data streams contain overhead bits that indicate the beginning of the DS3, DS1 and DS0 frames within such data streams. Accordingly, in addition to transmitting the DS0 data streams to interface unit 204, deframer unit 202 transmits signals indicating the beginning and ending points of these DS0 data streams (i.e., frame alignment data) based on the overhead bits contained in the DS3 and DS1 data streams. In other words, deframer unit 202 removes overhead bits, including framing bits, and transmits the payload (the DS0s data streams) along with frame alignment data indicating the beginning and ending points of the DS0 data streams to interface unit 204.
Interface unit 204 receives the interleaved DS0 data streams and formats such streams for processing by digital signal processor 206. Digital signal processor 206 receives the 24 interleaved DS0 data streams, which are effectively 24 separate telephone calls, and separates the DS0 data streams and creates 24 separate packet streams for subsequent packet processing and transmission. Moreover, digital signal processor 206 may compress some or all of 24 packet streams for subsequent transmission. Digital signal processor 206 then transmits these packet streams to packet processor 208. Packet processor 208 typically acts as a router using a forwarding table to router the packets through the network to the destined location.
Disadvantageously, line card 200 is typically located within a network element wherein the real estate for the racks holding the line cards of such network elements is considered to be expensive due to space limitations. In particular, such network elements are typically located a central office or on the premises of large customers. Accordingly, all of the hardware within line card 200, including interface unit 204 and digital signal processor 206, are considered very costly in terms of real estate. Moreover, digital signal processor 206 tends to consume a relatively large amount of power, which needs to be limited in this location. Moreover, digital signal processor 206 conventionally includes processing power that can handle more TDM signals than is provided at such locations.
FIG. 3 illustrates a prior art TDM switch for switching of DS0 data streams. This TDM switch, also termed a class 4 or class 5 switch, includes TDM bus 304, which is coupled to time-slot interchanger 302, (de)framer units 306-310 and DS0 interface 312. DS0 interface 312 is an interface that couples a number of DS0s from a number of different sources to TDM bus 304. For example, DS0 interface 312 could receive such DS0s from a Plain Old Telephone Service (POTS) line or to other sources that generate DS0s. (De)framer units 306-310 typically receive a number of DS3 and/or DS1 signals from external transmission lines and break such signals down into the DS0s contained therein. Additionally, a number of different DS0s are placed onto TDM bus 304 from (de)framer units 306-310 and DS0s 312. Such DS0s are then transmitted to time-slot interchanger 302 wherein the DS0s are re-ordered and routed back out from the TDM switch through (de)framer units 306-310 and DS0s 213.
For example, time-slot interchanger 302 could receive a first DS0 originating from a DS3 signal from (de)framer unit 306 and transmit this DS0 out (de)framer unit 310. Similarly, time-slot interchanger 302 could receive a second DS0 originating from a DS1 signal from (de)framer unit 308 and transmit this DS0 out (de)framer unit 310. Accordingly, (de)framer unit 310 could place these two DS0s along with 22 other DS0s into a DS1 signal and transmit this DS1 signal out from the TDM switch of FIG. 3. As illustrated, the TDM switch of FIG. 3 acts as a TDM cross-connect by allowing for the switching of TDM data at the DS0 level.